In 1982, Brezhnev, dictator of the Soviet Union, died and replaced by former KGB chief Yuri Andropov. In 1984 he dies and is replaced by Konstantin Chernenko. In 1895 he dies and is replaced by Mikhail Gorbechev. Gorbechev begins an anti-alcohol campaign and begins his policies of glasnost and perestroika. In 1986 Chernobyl occurs in the Ukraine in which radioactive material spreads over Europe. In 1987 The Soviet Union and US agree to destory intermediate range nuclear missiles. In 1988 Gorbechev challenges nationalists in Baltic States, Armenia, and Azerbaijan. In 1989 Soviet troops left Afghanistan, riots were put down in Georgia, and Lithuania declares independence. In 1990 the Baltic States declare independence. In 1991 many countries declare independence such as the Ukraine and Latvia. Gorbechev resigns and soon later the Soviet Uinion collapses.